Froth flotation



-by froth flotation.

Patented May 16, 1944 FBOTH FLOTATION- Thorbjern Hellmann, Copenhagen,Denmark, assignor to Separation Process Company, Catasauqua, Pa., acorporation of Delaware No Drawing. Application April 4,1941, Serial no.I

386,848. In Great Britain April 10, 1940 3 Claims.

This invention relates to the froth flotation of lime-bearing materials,and it is particularly"applicable to the cleaning of cement rawmaterials The flotation is brought about by the addition to theflotation pulp of reagents which act as frothing agents and collectin gagents, and usually different reagents are introduced for the twofunctions. The material that is treated in the flotation cells is oftenhighgrade slurry, and in such a case the amount of lime-bearingconcentrate that has to be removed as froth is usuallynot less than 50%of the material fed to the cells and often as much as 75%. It followsthat the frothing agents used must have a large frothing capacity. Itis, however, very important that the development of froth should not betoo violent, since, if it is, a large part of the minerals which shouldbe left in the reject will be carried out of the cells in theconcentrate.

It is naturally desirable to use reagents that are as cheap as possible,and this is particularly important because the comparatively low valueof the concentrate obtained from lime-bearing materials makes itsnecessary to use cheap reagents if the process is to be economicallypracticable. Accordingly, reagents prepared from waste materials, suchas those described in the pending application of M. Vogel-Jorgensen,Serial No. 230,342, filed September 16, 1938, may be used withadvantage. These reagents are derived from waste products obtained inthe refining of vegetable or animal oils, which as a rule are glyceridesof mixtures of fatty acids of different molecular weights, ,(some beingsaturated fatty acids and others unsaturated r oxidised fatty acids)together with unsaponifiable materiads. The reagents described in thesaid application which has now issued as U. S. Patent No. 2,216,992,under date of October 8, 1940, give surface active ions in water, andcomprise the products resulting from'the reaction of the waste productsremaining after the distillation of impure fatty acid oils produced inthe refining of a member from the group consisting of animal and fixedvegetable oils and fats for the recovery of refined fatty acid, with astrong alkali or a strong mineral acid, or the products resulting fromthe sulphonation or saponification of such products. They are collectingagents, but they also have so strong a'frothing capacity that theresults obtained with them are not entirely satisfactory in thetreatment of some raw materials, particularly those that are very finelydivided, as the concentrates are not of a high enough grade. There is aparticular tendency for froth to be produced too violently when thewater obtained from the subsequent dewatering of the concentrate iscirculated and used again in the flotation cells: This circulating watergenerallycontains a certain amount-of the reagents, so

that it is economical to use it again.

According to the present invention, the development of the frothproduced by the waste products referred to above or other collectingagents having too strong frothing action is controlled I by usingtogether with them hydrogen-saturated products, and which are alsousable in the form of saponified, sulphonated or similar products.Appropriate proportions of the froth controlling agent will varydepending on the frothing properties of the collecting agent and thepulp being treated. In the case of waste product collecting agents-ofthe above referred to type, 10 to parts of hydrogenated whale oil orbeef tallow should be used with every to parts of waste 2:5 oilderivative. In a specific case one part of the froth-controlling reagentwas used with every two parts of waste oil derivatives.

The fatty acids of high molecular weight are not suitable for use alone,firstly because a large quantity is required for collecting the limepar-,

ticles, much larger, indeed, than would be expected from-th differencein molecular weight, and still more because a large amount of froth-'-ing agent is required to obtain sufllcient lime in the overflow from theflotation machine. Their poor frothing capacity, however, makes them icapable of reducing the frothing capacity-of the Waste oils described inthe pending application Serial No. 230,342 referred to above by theaddition of a relatively small proportion of the fatty acids of highmolecular weight, so that the mixture is cheap and satisfactory.

When according to the invention reagents derived from productscontaining hydrogen saturated fatty acids of high molecularweight are.ter and 75% of fatty acids.

stated as suitable froth-controlling reagent to be used together withordinary reagents having too strong frothing action, it should beunderstood that the two types of reagents may be added to the pulpbefore and/or during the fio Often the fatty acids used for floating thelime-bearing minerals are used in the form of water-soluble soap and inthis case the fatty acids or the neutral fats or oils are saponifiedbefore they are used as flotation reagents. In such .case the two typesof reagents: the ordinary collecting reagent and the froth controllingfatty acid reagent, may be mixed before the saponification, the twoproducts saponified together thus giving a mixtureof the desiredfrothing properties. In other cases a partial saponification is used orfatty acids are emulsified before they are used as flotation reagents,and also in that event the two products may be mixed together before thefinal preparation of the reagents is carried out.

If waste product from the refining of the oils or fats are used asflotation reagents, either as the raw waste products or in a saponified,sulfonated, emulsified or similar state, the two types of raw oils orfats. may be refined together, either during the whole refining orduring the latter part of the refining, in which case a waste product isobtained which could be readily used or treated in a suitable way, thusgiving a flotation reagent of the desired frothing properties.

The following example will demonstrate the advantage of, using a wasteproduct containing a large amount of high molecular fatty acid togetherwith an ordinary type of waste oil. The test was made at a cement plantusing the flotation process. The raw material was a hard limestonecontaining about 80% CaCO: and amounts of wollastonite, which wereexcessive to make it useful for the manufacture of cement, for whichreason the limestone was cleaned by the flotation process. The raw stonewas ground in closed circuit with a gravity type hydraulic classifier tograin sizes below 0.2 m. 'm., and during normal operation at the plantthe slurry so produced was fed directly to the flotation cells. A sampleof this ground material was taken and most of the water contained in theslurry was removed by filtration. This material was used for the tests.One part of the filtered material was diluted with pure water to give asuspension of 300 g. of solids per litre and another part with the sameamount of overflow water from .the

thickener at the plant in which th concentrate from the flotation cellswas dewatered.

As collecting reagents were used the following types:

"Reagent A was waste oil of the type men-- tione'din pending applicationSerial No. 230,342 referred to above.

"Reagent B" was prepared from a waste product containing about 25% ofunsaponifiable mat- About 50% of these fatty acids was the highmolecular stearic acid, while the remaining part of the fatty acids waslower molecular fatty acids.

. the figures in tests Nos. 2 and 3.

alcohol frother.

The tests were carried out in a Fagergren laboratory flotation cell andthe so-called stage oiling method was used, which means that thereagents were added stepwise during the flotation. The results obtainedare given in the following During each flotation test was added the samekind of water as was used originally for diluting the filtered slurry.

Comparing the results fromtest No. 1 and test s No. 2 it will be seenthat the use of the overflow water from the thickener reduces the amountof collecting reagent considerably; however, the rade of the concentrateproduced in test No. 2. where the overflow water was used, iscomparatively low due to a too violent development of the froth in thecell. The small amount of 0.02% of the frothing reagent indicated in thetable had to be added during the very last part of this test in order toobtain a satisfactorily low grade of reject. In other words the type Areagent when used with overflow water had too strong frothing propertiesduring the first part of test No. 2

and too weak frothing properties during the last part.

Test No. 3, which is carried out with reagent B containing a high amountof fatty acids with high molecular weight, shows that a concentrate withhigh lime content is obtained, but at the same time a high reagentconsumption is required despite the fact that overflow water has beenused.

Test No. 4 shows that by using a reagent in accordance with thepresentinvention overflow water can be used whereby less reagent is re(wired and, nevertheless, the concentrate is high in 1 me.

The consumption of collecting and frothing agents in test No. 4 is aboutwhat could be calculated by proportioning from tests Nos. 2 and 3, butthecleanness of concentrate and reiect is substantially above what couldbe expected from Comparing test No. 4 with test No. 1 shows areductionin reagent consumption of 32%, the

cleanness of the concentrate remaining the same and the cleanness of therejects being improved.

I clilm:

1. In the flotation of lime-bearing minerala; the process of controllingthe frothing action of ucts remaining after the distillation of impure Ifatty acid oils produced in the refining of a member from the groupconsisting of animal and fixed vegetable oils and fats for the recoveryof refined fatty'acid, with a strong mineral acid. the compoundsresulting from the sulphonation As frothing reagent was used a highmolecular from the group consisting of animal and fixed vegetable oilsand fats for the recovery of refined .tatty acid, with a strong alkali,by using together with them hydrogen-saturated fatty acids 0! highmolecular weight containing not less than 16 and not more than 18 carbonatoms.

3. In the flotation of lime-bearing minerals, the process of controllingthe frothing action of collecting reagents which in water give surfaceactive ions, and which comprise the products resulting from the reactionof the waste products remaining after the distillation of impure fattyacid oils produced in the refining of a member from the group consistingof animal and fixed vegetable oils and fats for the recovery of refinedfatty acid, with a strong alkali, by using together with them saponifledhydrogen-saturated fatty acids of high molecular weight containing notless than 16 and not more than 18 carbon atoms.

THORBJQZRN HEILMANN.

